This invention relates to a sieve drum device for the flow-through heat treatment of a gas-permeable length of material, especially textile material, said device having a substantially closed housing, the inner space of which is subdivided by a wall into a treatment chamber and a fan chamber; at least one sieve drum which is under a suction draft which is covered in the peripheral zone not blanketed by the material and which is rotatably mounted in the treatment chamber as a conveying element; and a fan in the fan chamber at the end face side associated with this sieve drum, this fan blowing a treatment gas suctioned out of the sieve drum, after heating by means of an associated heating unit, again back into the treatment chamber via a perforated screen cover concentrically surrounding the sieve drum. The device including means for effecting movement of the perforated screen cover.
A similar device is known from DOS 3,006,758. A screen cover concentrically surrounding the sieve drum has the advantage that the air flowing to the sieve drum is not only dammed up by the screen cover, but it is also caused to blow more uniformly over the periphery onto the sieve drum. However, this construction has the disadvantage that, if any material to be treated should jam up on the sieve drum, a knot could be formed perhaps in the narrowed space between the screen cover and the sieve drum and then untangling of this know would hardly be possible. Also, cleaning of the screen cover is feasible only under conditions that are made difficult because the screen cover surrounds the sieve drum closely all around and thus cleaning utensils cannot reach the underside of the screen cover.